Introduce Group Types API.
Modeled on the Member Types API, Group Types allow developers to register
arbitrary group categorizations, and assign one or more of these types to a
given group. BuddyPress stores this information in a custom taxonomy on the
root blog.
Group queries can be filtered by group type, by using the group_type,
group_type__in, and group_type__not_in parameters in the bp_has_groups()
template loop function stack.
Props Mamaduka, boonebgorges, dcavins.
See #6784.